1. Field of the Invention
The present invention relates to a structure having a photonic crystal, and a surface-emitting laser including a structure having a photonic crystal.
2. Description of the Related Art
In recent years, many examples of photonic crystals applied to semiconductor lasers have been reported. Japanese Patent Application Laid-Open No. 2000-332351 discloses a surface-emitting laser light source in which an active layer containing a light-emitting material is provided and a two-dimensional photonic crystal is formed in the vicinity of the active layer.
This two-dimensional photonic crystal is periodically provided with a columnar hole on a semiconductor layer, and has two-dimensional periodicity in distribution of a refractive index.
Because of this periodicity, the light generated in the active layer is resonated in harmony, and forms a stationary wave, thereby to perform a laser oscillation.
Further, the light is extracted in the perpendicular direction to the plane by primary diffraction, thereby to be allowed to work as a surface-emitting laser.
In the surface-emitting laser including such a photonic crystal, when a size of the two-dimensional photonic crystal is limited, a leakage of the light occurs in an in-plane direction. Such a leaked light in the in-plane direction causes losses, and leads to the increase in oscillation threshold value and the lowering of an optical output.
Hence, heretofore, Japanese Patent Application Laid-Open No. 2003-273456 has proposed a two-dimensional photonic crystal light-emitting laser in which a structure allowing the light leaked in the in-plane direction to reflect by using a photonic band gap is disposed around a two-dimensional photonic crystal.
As a result, the light leaking in the in-plane direction is returned to the inside of a region of the two-dimensional photonic crystal.
As described above, in the photonic crystal surface-emitting laser, when a size of the two-dimensional photonic crystal is limited, a leakage of the light occurs in the in-plane direction.
To prevent this leakage, when the photonic crystal is made large, there arises a problem that a size of the device becomes large.
Further, similarly to Japanese Patent Application Laid-Open No. 2003-273456, even in the case that the structure reflecting the light leaked in the in-plane direction is disposed around the photonic crystal, the following problem occurs.
That is, Japanese Patent Application Laid-Open No. 2003-273456 employs a structure wherein the light leaked in the in-plane direction is reflected by utilizing the photonic band gap.
In such a structure, since the light is reflected by multiple reflection by a periodic structure, as the necessary reflectance is increased, the necessary number of periods is increased, and as a result, there arises a problem that the size ends up becoming large.
In view of the above described problem, an object of the present invention is to provide a structure having a photonic crystal capable of reflecting efficiently the light leaked in the in-plane direction in small size and being re-used and a surface-emitting laser including a structure having a photonic crystal.